U.S. patent application number 11/407510 was filed with the patent office on 2006-10-26 for exhaust system and control method for an internal combustion engine.
Invention is credited to Sunki I, Takao Inoue, Kouichi Mori.
Application Number | 20060236682 11/407510 |
Document ID | / |
Family ID | 36570393 |
Filed Date | 2006-10-26 |
United States Patent
Application |
20060236682 |
Kind Code |
A1 |
I; Sunki ; et al. |
October 26, 2006 |
Exhaust system and control method for an internal combustion
engine
Abstract
An exhaust system for an internal-combustion engine comprises an
exhaust bypass in parallel with an upstream portion of a main
exhaust path having a main catalytic converter in a downstream
portion thereof, an exhaust bypass catalytic converter provided in
the exhaust bypass; and a flow path switching valve for blocking
the main exhaust path at the upstream portion thereof. The exhaust
system includes an ignition timing adjustment mechanism for
adjusting ignition timing to delay sparking when the flow path
switching valve is switched from the closed condition to the open
condition thereof. A control method for the exhaust system is also
disclosed.
Inventors: |
I; Sunki; (Kanagawa, JP)
; Inoue; Takao; (Kanagawa, JP) ; Mori;
Kouichi; (Kanagawa, JP) |
Correspondence
Address: |
RADER, FISHMAN & GRAUER PLLC
39533 WOODWARD AVENUE
SUITE 140
BLOOMFIELD HILLS
MI
48304-0610
US
|
Family ID: |
36570393 |
Appl. No.: |
11/407510 |
Filed: |
April 20, 2006 |
Current U.S.
Class: |
60/288 ;
60/285 |
Current CPC
Class: |
Y02T 10/47 20130101;
F02D 2041/0067 20130101; Y02T 10/40 20130101; F02D 41/1441
20130101; F02P 5/1502 20130101; F02D 35/025 20130101; F02D 41/024
20130101; F01N 2430/08 20130101; F01N 3/2053 20130101; F01N 9/00
20130101; F01N 2410/06 20130101; Y02T 10/12 20130101; Y02T 10/22
20130101; F01N 13/0093 20140601; F02D 41/0065 20130101; Y02T 10/46
20130101; F01N 3/20 20130101; F01N 3/101 20130101; F01N 13/009
20140601 |
Class at
Publication: |
060/288 ;
060/285 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2005 |
JP |
2005-123101 |
Claims
1. An exhaust system for an internal-combustion engine comprising:
an exhaust bypass that is positioned in parallel with an upstream
portion of a main exhaust path having a main catalytic converter in
a downstream portion thereof; an exhaust bypass catalytic converter
provided in the exhaust bypass; and a flow path switching valve
capable of blocking the main exhaust path at the upstream portion
thereof; and wherein the exhaust system includes an ignition timing
adjustment mechanism for adjusting ignition timing when the flow
path switching valve is switched.
2. An exhaust system for an internal-combustion engine according to
claim 1, wherein the ignition timing adjustment mechanism retards
the ignition timing when the flow path switching valve is switched
from a closed condition to an open condition thereof.
3. An exhaust system for an internal-combustion engine according to
claim 2, wherein the ignition timing delay becomes greater as the
size of an aperture defined by the flow path switching valve
increases.
4. An exhaust system for an internal-combustion engine according to
claim 2, wherein a path resistance of the main exhaust path is
lower than a path resistance of the exhaust bypass when the flow
path switching valve is in the open condition thereof.
5. An exhaust system for an internal-combustion engine according to
claim 2, further comprising a throttle valve aperture adjustment
mechanism for adjusting a throttle valve aperture; wherein the
throttle valve aperture is adjustable in a decreasing direction by
the throttle valve aperture adjustment mechanism when the flow path
switching valve is switched from the closed condition to the open
condition thereof.
6. An exhaust system for an internal-combustion engine according to
claim 5, wherein the throttle valve aperture becomes smaller as the
size of an aperture defined by the flow path switching valve
increases.
7. An exhaust system for an internal-combustion engine according to
claim 2, further comprising an exhaust recirculation amount
adjustment mechanism for adjusting an amount of the exhaust
recirculation; wherein the amount of exhaust recirculation is
adjustable in the increasing direction by the exhaust recirculation
amount adjustment mechanism when the flow path switching valve is
switched from the closed condition to the open condition
thereof.
8. An exhaust system for an internal-combustion engine according to
claim 7, wherein the amount of exhaust recirculation becomes
greater as the size of an aperture defined by the flow path
switching valve increases.
9. An exhaust system for an internal-combustion engine according to
claim 2, wherein an amount of fuel supplied to the internal
combustion engine is adjustable in the increasing direction when
the flow path switching valve is switched from the closed condition
to the open condition thereof.
10. An exhaust system for an internal-combustion engine according
to claim 9, wherein the amount of fuel becomes greater as the size
of an aperture defined by the flow path switching valve
increases.
11. An exhaust system for an internal-combustion engine according
to claim 9, wherein an engine air-fuel ratio based on an amount of
intake air is adjustable in the richer direction by increasing the
amount of fuel when the flow path switching valve is opened,
thereby canceling out leanness of an exhaust air-fuel ratio at an
entrance of the main catalytic converter.
12. An exhaust system for an internal-combustion engine according
to claim 11, wherein the engine air-fuel ratio becomes richer as
the size of an aperture defined by the flow path switching valve
increases.
13. An exhaust system for an internal-combustion engine comprising:
means for bypassing exhaust gases in parallel with an upstream
portion of a main exhaust path having a main catalytic converter in
a downstream portion thereof; means associated with said bypassing
means for purifying the bypassed gases; and valve means capable of
blocking the main exhaust path at the upstream portion thereof; and
means for adjusting ignition timing to delay sparking when the
valve means is switched from a blocking condition to an unblocking
condition.
14. A control method for an exhaust system of an
internal-combustion engine, the exhaust system comprising:
providing an exhaust bypass in parallel with an upstream portion of
a main exhaust path having a main catalytic converter in a
downstream portion thereof; providing an exhaust bypass catalytic
converter in the exhaust bypass; and providing a flow path
switching valve capable of blocking the main exhaust path at the
upstream portion thereof; and adjusting ignition timing to delay
sparking when the flow path switching valve is switched from a
closed condition to an open condition thereof.
15. A control method for an exhaust system of an
internal-combustion engine according to claim 14, wherein the
adjusting amount of the delay of ignition timing is increased as
the size of an aperture defined by the flow path switching valve
increases.
16. A control method for an exhaust system of an
internal-combustion engine according to claim 14, wherein a path
resistance of the main exhaust path is lower than a path resistance
of the exhaust bypass when the flow path switching valve is
switched to the open condition thereof.
17. A control method for an exhaust system of an
internal-combustion engine according to claim 14, further
comprising: adjusting a throttle valve to decrease a throttle valve
aperture when the flow path switching valve is switched from the
closed condition to the open condition thereof.
18. A control method for an exhaust system of an
internal-combustion engine according to claim 17, wherein the
throttle valve aperture is decreased in size as the size of an
aperture defined by the flow path switching valve increases.
19. A control method for an exhaust system of an
internal-combustion engine according to claim 14, including
adjusting the amount of exhaust recirculation in the increasing
direction when the flow path switching valve is switched from the
closed condition to the open condition thereof.
20. A control method for an exhaust system of an
internal-combustion engine according to claim 19, wherein the
amount of exhaust recirculation is enlarged as the size of an
aperture defined by the flow path switching valve is increased.
21. A control method for an exhaust system of an
internal-combustion engine according to claim 14, including
adjusting an amount of fuel supply to the internal-combustion
engine in the increasing direction when the flow path switching
valve is switched from the closed condition to the open condition
thereof.
22. A control method for an exhaust system of an
internal-combustion engine according to claim 21, wherein the
amount of fuel supply is enlarged as the size of an aperture
defined by the flow path switching valve increases.
23. A control method for an exhaust system of an
internal-combustion engine according to claim 21, including
adjusting an engine air-fuel ratio based on the amount of intake
air in the richer direction by increasing the amount of fuel when
the flow path switching valve is opened, thereby canceling out
leanness of an exhaust air-fuel ratio at an entrance of the main
catalytic converter.
24. A control method for an exhaust system of an
internal-combustion engine according to claim 23, wherein the
engine air-fuel ratio is enriched as the size of an aperture
defined by the flow path switching valve increases.
Description
RELATED APPLICATION
[0001] The disclosure of Japanese Patent Application No. Japanese
Application No. 2005-123101, filed Apr. 21, 2005, including the
specification, claims and drawings, is incorporated herein by
reference in its entirety.
FIELD
[0002] Described herein is an exhaust system for an
internal-combustion engine in which, by operating a flow path
switching valve upon a cold start, the exhaust gases are guided to
an exhaust bypass having an exhaust bypass catalytic converter
upstream relative to the exhaust system. Also described herein is
an adjustment control method carried out upon operation of the flow
path switching valve.
BACKGROUND
[0003] Structure is known in which a main catalytic converter at
the underbody of a vehicle is disposed downstream of an exhaust
system of the vehicle's internal-combustion engine. With this
arrangement, sufficient exhaust purification cannot be expected
after starting the engine under cold conditions until the catalytic
converter is activated with its temperature raised. In contrast, if
the catalytic converter were arranged upstream relative to the
exhaust system; that is, closer to the engine, durability would be
reduced due to thermal deterioration of the catalyst.
[0004] Therefore, as disclosed in Japanese Laid-Open Patent
Application No. H05-321644, proposals have been made for an exhaust
system in which an exhaust bypass is provided parallel to the
upstream portion of the main exhaust path in which there is a main
catalytic converter, and another catalytic converter is provided in
the exhaust bypass, the exhaust gases being guided to the exhaust
bypass immediately after starting under cold conditions by means of
a switching valve that switches between the main exhaust path and
the exhaust bypass. With this structure, the exhaust bypass
catalytic converter is located upstream relative to the main
catalytic converter, and exhaust purification can be commenced at
an earlier stage because catalyst activation is carried out at a
relatively early stage.
SUMMARY
[0005] The present exhaust system for an internal-combustion engine
comprises an exhaust bypass in parallel with the upstream portion
of a main exhaust path having a main catalytic converter in its
downstream portion. An exhaust bypass converter is provided in the
exhaust bypass, and a flow path switching valve is provided for
blocking the main exhaust path at its upstream portion when the
valve is in a closed position. An ignition timing device is also
provided for adjusting the ignition timing to delay ignition when
the switching valve is moved from its closed position to its open
position.
BRIEF DESCRIPTION OF DRAWINGS
[0006] These and other features and advantages of the present
exhaust system and control method will be apparent from the ensuing
description taken in conjunction with the accompanying drawings, in
which:
[0007] FIG. 1 is a schematic view showing the layout of an
embodiment of the present exhaust system;
[0008] FIGS. 2A-2I are a series of time charts showing an example
of the present control method, in which the flow path switching
valve is open during normal operation;
[0009] FIGS. 3A-3G are a series of time charts showing an example
of the present control method, in which the flow path switching
valve is opened during moderate acceleration; and
[0010] FIGS. 4A-4G are a series of time charts showing an example
of the present control method, in which the flow path switching
valve is opened upon an increase in load.
DETAILED DESCRIPTION
[0011] An embodiment of the present exhaust system and control
method is hereinafter described in detail as being applied to a
serial four-cylinder internal-combustion engine.
[0012] Referring to FIG. 1, a combustion chamber 22 is formed by a
cylinder bore provided in a cylinder block 13, a cylinder head 1
attached to the cylinder block, and a piston 14 received in the
cylinder bore. Air regulated by a throttle valve 16 is supplied to
the combustion chamber 22 from an inlet path 23 at the same time
that fuel is injected in the combustion chamber 22 by a fuel
injection valve 17. Exhaust gases adjusted by an EGR valve 19 are
recirculated to the inlet path 23 via an EGR path 20. The air-fuel
mixture formed by the air and fuel supplied to the combustion
chamber 22 is ignited by sparking an ignition plug 18. A
temperature sensor 21 provided on the cylinder block 13 detects the
engine temperature (temperature of the coolant). The exhaust gases
resulting from combustion are discharged from the combustion
chamber 22 via an exhaust port 2.
[0013] Exhaust ports 2 for each of a series of four like cylinders
are provided on a lateral side of the cylinder head 1. Main exhaust
paths 3 are connected to each of the exhaust ports 2. The four main
exhaust paths 3 for the respective cylinders are joined in a single
flow path, and a main catalytic converter 4 is arranged in the
downstream side thereof. The main catalytic converter 4 has a large
capacity and is disposed at the underbody of the vehicle; it
contains, for example, a three-way catalyst and an HC trap
catalyst. The main exhaust paths 3 and main catalytic converter 4
comprise the main flow path for the exhaust gases during normal
operation. In addition, a flow path switching valve 5 that opens
and closes each of the main exhaust paths 3 simultaneously is
provided at the junction of the four main exhaust paths 3.
[0014] An exhaust bypass 7 having a smaller cross-sectional area
than that of each of the main exhaust paths 3 branches out from
each of them. A branching point 6 at the upstream end of each
bypass 7 is arranged as far upstream as possible of the main
exhaust path 3. The four bypasses 7 eventually join into a single
flow path at their downstream ends, and an exhaust bypass catalytic
converter 8 using a three-way catalyst is provided immediately
downstream of the point at which they join. The exhaust bypass
catalytic converter 8 is of compact form, having a smaller capacity
than that of the main catalytic converter 4, and it preferably
includes a catalyst having superior activity at low temperatures.
The downstream portion of the exhaust bypass, which extends from
the exit end of the exhaust bypass catalytic converter 8, is
connected to the upstream portion of the main catalytic converter 4
in the main exhaust path 3 at a junction 12 (whereby the flow path
switching valve 5 is upstream of the junction 12).
[0015] Air-fuel ratio sensors 10 and 11 are provided respectively
at the entrance of the main catalytic converter 4 and at the
entrance of the exhaust bypass catalytic converter 8. The flow path
switching valve 5, air-fuel ratio sensors 10 and 11, throttle valve
16, fuel injection valve 17, ignition plug 18, EGR valve 19, and
temperature sensor 21 are all connected to the controller 15. The
controller regulates the aperture of the flow path switching valve,
the intake air amount, the fuel injection amount, the ignition
timing, the EGR amount, etc., based on the detected engine
temperature and the exhaust air-fuel ratio.
[0016] During the stage in which the temperature of the engine or
the exhaust gases is relatively low immediately after a cold start,
the flow path switching valve 5 is closed by means of an
appropriate actuator, and thus the main exhaust path 3 is blocked.
Therefore the entire volume of the exhaust gases discharged from
each cylinder flows into the exhaust bypass 7 via the branching
point 6, and thence to the exhaust bypass catalytic converter 8.
The exhaust bypass catalytic converter 8, being located at the
upstream portion of the exhaust system close to the exhaust port 2,
and being of compact form, is immediately activated and begins
exhaust purification at an early period.
[0017] When the warming of the engine progresses and the
temperature of the engine or the exhaust gases becomes sufficiently
high, the flow path switching valve 5 is opened. When this occurs,
the exhaust gases discharged from each cylinder pass mostly through
the main exhaust path 3 to the main catalytic converter 4. At this
time, the exhaust bypass 7 is not necessarily blocked; nonetheless,
since the exhaust bypass 7 has a smaller cross-sectional area than
that of the main exhaust path 3, and since the exhaust bypass
catalytic converter 8 is provided in the exhaust bypass, therefore,
due to the difference in path resistance, a major portion of the
exhaust gases flows through the main exhaust path 3 and there is
very little flow through the exhaust bypass 7. Thus, thermal
deterioration of the exhaust bypass catalytic converter 8 is
satisfactorily limited.
[0018] When the flow path switching valve 5 opens the main exhaust
path 3, as described above, the path resistance of the main exhaust
path 3 is relatively low, so that the exhaust pressure rapidly
decreases and if it remains as is, uneven torque, namely an
increase in torque is generated. In addition, when the switching
valve 5 opens the main exhaust path 3, the thin exhaust gas, which
is close to the atmospheric state, and which has accumulated in the
main exhaust path 3, flows into the main catalytic converter 4
downstream, and consequently the exhaust air-fuel ratio in the main
catalytic converter 4 temporarily becomes relatively lean, thereby
temporarily reducing the exhaust purification performance of the
three-way catalyst.
[0019] Therefore, according to the present control method, the
uneven torque is eased by delaying sparking by means of the
ignition timing when the flow path switching valve 5 opens, and at
the same time, the tendency of the exhaust air-fuel ratio to become
lean is limited by increasing the amount of fuel injection.
[0020] FIGS. 2A-2I are a series of time charts that explain a
variety of the operations described above. This is an example in
which the flow path switching valve 5 is open during normal
operation. In this figure, interrupted lines show properties when
the present control is not employed and solid lines show such
properties when the present control is employed. As shown FIG. 2A,
when warming of the engine is completed, the flow path switching
valve 5 is open, and as shown in FIG. 2B, the exhaust pressure
decreases. Because of this, the amount of gas flow at the entrance
of the main catalytic converter 4 increases as shown in FIG. 2C.
Here the shaded portion in FIG. 2C is the increase due to the gas
accumulated between the branching point 6 and the junction 12 with
the main exhaust path 3. For such a change, according to the
present embodiment, sparking is temporarily adjusted by delaying
ignition timing as shown by the solid line in FIG. 2E. At the same
time, the aperture of the electronically controlled throttle valve
in the inlet path is temporarily adjusted to decrease the amount of
the intake air as shown by the solid line in FIG. 2D. At the same
time, the exhaust flux rate of the exhaust recirculation system not
shown in the figure is adjusted to increase as shown by the solid
line in FIG. 2F. Due to the above-mentioned adjustment, the torque
generated by the internal-combustion engine is flat; that is, there
is no uneven torque, as shown by the solid line in FIG. 2G.
[0021] In addition, the amount of fuel injection is temporarily
adjusted to increase as shown by the solid line in FIG. 2I, and
consequently the exhaust air-fuel ratio at the entrance of the main
catalytic converter 4 has a flat property as shown by the solid
line in FIG. 2H. In other words, the air-fuel ratio in the
combustion chamber of the engine becomes temporarily rich compared
to the theoretical air-fuel ratio, thereby canceling the effect of
the accumulated gases close to the atmospheric state. By doing so,
desirable exhaust purification performance of the three-way
catalyst of the main catalytic converter can be obtained.
[0022] FIGS. 3A-3G are a series of time charts similar to those of
FIGS. 2A-2I. It shows, in particular, the case in which the flow
path switching valve 5 opens during moderate acceleration of the
internal-combustion engine. In this case, similarly to the
above-explained example in FIGS. 2A-2I, uneven torque is eased by
delayed sparking of the ignition timing, the limiting of the amount
of intake air, and the increase in the exhaust recirculation rate,
and as shown by the solid line in FIG. 3G, the torque moderately
increases as directed by the driver. In addition, by increasing the
amount of fuel injection, the tendency of the exhaust air-fuel
ratio to become relatively lean at the entrance of the main
catalytic converter 4.
[0023] In principle, the flow path switching valve 5 is, as
described above, switched from the closed condition to the opened
condition in response to the warming of the engine, namely the
activation of the main catalytic converter 4; nonetheless, even
before the main catalytic converter 4 is activated, if the
requested load exceeds a designated level, it is switched to the
open condition in order to avoid a reduction in torque due to
air-flow resistance.
[0024] FIGS. 4A-4G are a series of time charts and shows an example
of engine operation. FIG. 4A is engine revolution, FIG. 4B is
vehicle speed, FIG. 4C is the accelerator aperture, FIG. 4D is the
throttle valve aperture, FIG. 4E is the catalyst activity
determination flag for the main catalytic converter 4, FIG. 4F is
the state of the flag that permits the opening of the flow path
switching valve 5, and FIG. 4G is the aperture of the flow path
switching valve 5. As shown in FIGS. 4A-4G, when the aperture of
the throttle valve (or the aperture of the accelerator) becomes
larger than a predetermined aperture size, the flag that permits
opening becomes active 1 even before activation of the catalyst and
the flow path switching valve 5 opens. Therefore the exhaust
pressure is reduced and the requested torque is maintained. In
addition, when such a high-load state is not detected, when the
catalyst activation determination flag that indicates activation of
the catalyst becomes active 1, the flow path switching valve 5
opens as shown by an interrupted line.
[0025] Therefore the present exhaust system structure comprises an
exhaust bypass provided in parallel with the upstream portion of a
main exhaust path having a main catalytic converter at its
downstream portion; an exhaust bypass catalytic converter provided
in the exhaust bypass; and a flow path switching valve that blocks
the main exhaust path at its upstream portion, wherein the ignition
timing is adjusted to delay sparking when the flow path switching
valve is switched from the closed condition to the open condition.
By doing so, the torque of the internal-combustion engine is
temporarily reduced, thereby easing uneven torque.
[0026] For example, the path resistance of the main exhaust path
when the above-mentioned flow path switching valve is in its open
condition is lower than the path resistance of the exhaust bypass.
In this case, the change in exhaust pressure is relatively great
when the flow path switching valve is switched from its closed to
its open condition; nonetheless, uneven torque can be limited with
good responsiveness by adjusting the ignition timing to delay
sparking.
[0027] In order to ease uneven torque, it is acceptable to
temporarily adjust the throttle valve aperture in the decreasing
direction. Alternatively, the amount of the exhaust recirculation
can be temporarily adjusted in the increasing direction.
[0028] In addition, the amount of the fuel supply can be
temporarily adjusted in the increasing direction in order to avoid
deterioration of exhaust purification performance due to flowing of
relatively thin exhaust gases close to the atmospheric state, which
have accumulated in the main exhaust path, into the main catalytic
converter. For example, the engine air-fuel ratio based on the
amount of intake air is adjusted on the rich side so that it
cancels out the leanness of the exhaust air-fuel ratio at the
entrance of the main catalytic converter when the flow path
switching valve opens. This avoids making the exhaust air-fuel
ratio relatively lean at the entrance of the main catalytic
converter when the flow path switching valve opens the main exhaust
path, thereby maintaining the exhaust air-fuel ratio at the amount
equivalent to a predetermined air-fuel ratio, and consequently
desirable exhaust purification performance can be obtained.
[0029] According to an embodiment of the present exhaust system and
control method, each of the adjustment amounts becomes greater as
the aperture of the flow path switching valve enlarges. When the
flow path switching valve is reaches a fully open condition, the
amount of the adjustment decreases.
[0030] According to the present exhaust system and control method,
when the flow path switching valve that switches the flow path
between the main exhaust path and the exhaust bypass is switched to
an open condition from a closed condition, a large uneven torque
due to the change in the exhaust pressure is not generated, and in
addition, a temporary reduction of the exhaust purification
performance of the main catalytic converter can be avoided. In
other words, the exhaust purification performance immediately after
a cold start can be improved without having an adverse effect on
operability or exhaust purification performance after the engine
has warmed.
[0031] While this invention has been described with respect to an
embodiment where the flow path switching valve is opened from a
closed condition, it is understood that this invention may also be
applied by in the opposite direction where the flow path switching
valve is closed from an open condition.
[0032] While the present exhaust system and control method have
been described in connection with a certain specific embodiment
thereof, this is by way of illustration and not of limitation, and
the appended claims should be construed as broadly as the prior art
will permit.
* * * * *